The purpose of this work is to examine the dynamic properties of macromolecules and macromolecular aggregates, using temperature-jump relaxation kinetics. The mechanism of thermal unfolding of RNA molecules will be studied by these methods, yielding information on the nature of the secondary structure, the existence of tertiary structure and the mechanism of structural changes. The dynamics of macromolecular association reactions will be studied, especially the association of histones with DNA and with other histones. These reactions will be detected by time-dependent light scattering measurements. BIBLIOGRAPHIC REFERENCES: Localization of the Structural Change Induced in tRNA fMet (Escherichia coli) by Acidic pH, M. Bina-Stein and D.M. Crothers, Biochemistry 14, 4185 (1975). Binding Kinetics of Mercury (II) to Polynucleotides, M.N. Williams and D.M. Crothers, Biochemistry 14, 1944-1951 (1975).